Typical multi-layered vacuum super insulated cryogenic tanks utilize a pair of cylindrical inner and outer tanks that are arranged concentrically with the inner tank residing in an interior of the outer tank. There are multiple radiant heat shields, approximately 30–80, coiled around the inner tank between the inner and outer tanks. A high vacuum exists between the inner and outer tanks to further prevent heat transfer. This type of thermal insulation is called a multi-layered vacuum super insulation. These storage tanks are capable of storing fluids at cryogenic temperatures.
The inner tank is positioned within the outer tank so that the inner tank does not contact the outer tank and so that thermal conduction paths between the inner and outer tanks are minimized. To facilitate this positioning, the inner tank typically has a pair of closed end pipes welded on opposite ends of the inner tank that form closed end channels that extend into the interior of the inner tank. A pair of rods are positioned in the channels to support the inner tank within the outer tank. The rods are designed so that the only contact between the rods and the inner tank is the interface between the ends of the rods and the ends of the channels. Opposite ends of the rods are attached to the internal surface of the outer tank. The rods, positioned on opposite ends of the inner tank, thereby support the inner tank within the outer tank.
To minimize the conductive heat paths, the rods are made from a carbon or glass fiber or other composite material. The carbon and glass fibers provide low thermal conductivity and help to isolate the inner tank from the outer tank. To further reduce the possibility of heat conduction between the inner and outer tanks, the rods can be made longer. That is, the length that the channels extend into the interior cavity of the inner tank can be increased, which decreases the volume of the inner tank, to allow for longer rods to be employed without increasing the dimensions of the outer tank. However, as the rods get longer, the bending force on the rods increases and a larger diameter rod is required to support the load over the longer distance. This in turn requires a larger surface area for the contact between the rods and the inner tank which increases the amount of heat being conducted through the rods, thus there is a trade-off between the conduction caused by the length of the rod and the conduction caused by the increased surface area of the rods in contact with the ends of the channel to support the loading caused by the extended length. Accordingly, it would be advantageous to provide an apparatus for supporting the inner tank within the outer tank that has a minimal intrusion on the inner tank while also limiting the conductive heat paths between the inner and outer tanks.
With the advent of fuel cell technology and the inclusion of fuel cells on mobile platforms (i.e. vehicles), there is a need for an onboard hydrogen storage system. The space in which to provide for hydrogen storage on the mobile platforms is limited. Additionally, the available space may be irregular in shape. The typical cryogenic storage tanks, as discussed above, are cylindrical. The cylindrical shape is used because it provides for cancellations of the forces applied to/on the storage tank. However, the use of a cylindrical cryogenic tank on a mobile platform may not provide the most efficient use of the available space on the mobile platform. Accordingly, it would be advantageous to provide a cryogenic storage tank that is non-cylindrical in shape. Furthermore, it would be advantageous to provide a cryogenic storage tank that is capable of more closely conforming to the available space on the mobile platform to maximize the amount of fluid that can be stored in the cryogenic tank on the mobile platform within the available space.